Vietnamese phonology

The phonology of Vietnamese features 19 consonant phonemes, with 5 additional consonant phonemes used in Vietnamese's Southern dialect, and 4 exclusive to the Northern dialect. Vietnamese also has 14 vowel nuclei, and 6 tones that are integral to the interpretation of the language. Older interpretations of Vietnamese tones differentiated between "sharp" and "heavy" entering and departing tones. This article is a technical description of the sound system of the Vietnamese language, including phonetics and phonology. Two main varieties of Vietnamese, Hanoi and Saigon, which are slightly different to each other, are described below.

Initial consonants which exist only in the Northern dialect are in red, while those that exist only in the Southern dialect are in blue.

• /w/ is the only initial consonant permitted to form consonant clusters with other consonants.
• /p/ occurs syllable-initially mostly in loan words, some speakers pronounce it as /ɓ/ (as in sâm panh, derived from French champagne).
• The glottalized stops are preglottalized and voiced: [ʔɓ, ʔɗ] (the glottis is always closed before the oral closure). This glottal closure is often not released before the release of the oral closure, resulting in the characteristic implosive pronunciation. However, sometimes the glottal closure is released prior to the oral release in which case the stops are pronounced [ʔb, ʔd]. Therefore, the primary characteristic is preglottalization with implosion being secondary.
• /ɓ, m/ are bilabial, while /f, v/ are labiodental.
• /t, tʰ/ are denti-alveolar ([t̪, t̪ʰ]), while /ɗ, n, l/ are apico-alveolar.^[1]
• /c, ɲ/ are phonetically lamino-palatoalveolar (the blade of the tongue makes contact behind the alveolar ridge).
• /ʈ, c/ are often slightly affricated [ʈ͡ʂ, t͡ɕ], but they are unaspirated.
• A glottal stop [ʔ] is inserted before words that begin with a vowel or /w/:

• d, gi and r are all pronounced /z/. But in some families, people still pronounce r as /ʀ/ or r in English^{[clarification needed]}, which is pretty rare.
• ch and tr are both pronounced /c/, while x and s are both pronounced /s/.
• Some rural speakers merge /l/ and /n/ into /l/ or the opposite to /n/, although this is not considered standard.^[1]

• d and gi are both pronounced /j/.
• Historically, /v/ is pronounced [j] in common speech, merging with d and gi. However, it is becoming distinct and pronounced as [v], especially in careful speech or when reading a text. In traditional performance including Cải lương, Đờn ca tài tử, Hát bội and some old speakers of Overseas Vietnamese, it is pronounced as consonant cluster [bj], [βj] or [vj].^[2] In loanwords, it is always pronounced [v]: va li [vaː˧ lɪi̯˧].
• Historically, a distinction is made between ch /c/ and tr /ʈ/, as well as between x /s/ and s /ʂ/. However, in many speakers, these two pairs are becoming merged as /c/ and /s/ respectively.^[3]
• In informal speech, /kw/, /hw/, /ʔw/, and sometimes /ŋw/ are pronounced [w]. However, it is becoming distinct and pronounced as [kw], [hw], [w], [ŋw] respectively, especially in formal speech or when reading a text.
• In southern speech, the phoneme /r/, generally represented in Vietnamese linguistics by the letter ⟨r⟩, has a number of variant pronunciations. It may occur as a retroflex fricative [ʐ], an alveolar fricative [z], a velar fricative [ɣ], a palatal approximant [j], or a trill [r].^[4]

The table below summarizes these sound correspondences:

The IPA chart of vowel nuclei above is based on the sounds in Hanoi Vietnamese; other regions may have slightly different inventories. Vowel nuclei consist of monophthongs (simple vowels) and three centering diphthongs.

• All vowels are unrounded except for the four back rounded vowels: /u, o, ɔ, uə̯/.
• In the South, the high vowels /i, ɨ, u/ are all diphthongized in open syllables: [ɪi̯, ɯ̽ɯ̯, ʊu̯], Ba Vì [baː˧ vɪi̯˩] (listen^ⓘ).^[5]
• /ə̆/ and /ă/ are pronounced shorter than the other vowels. These short vowels only occur in closed syllables.
• The vowels /ɛː/ and /ɔː/ are marginal. As with the other short/long vowel pairs, short and long /ɛ/ and /ɔ/ are only distinguished in closed syllables. For some speakers the distinction may be one of vowel quality or of the articulation of the syllable coda in addition to or instead of vowel quantity.^[6]
• /ɨ/: Many descriptions, such as Thompson,^[7] Nguyễn (1970), Nguyễn (1997), consider this vowel to be close back unrounded: [ɯ]. However, Han's^[8] instrumental analysis indicates that it is more central than back. Hoang (1965), Brunelle (2003) and Phạm (2006) also transcribe this vowel as central.

In Vietnamese, vowel nuclei are able to combine with offglides /j/ or /w/ to form closing diphthongs and triphthongs. Below is a chart^[9] listing the closing sequences of general northern speech.

Thompson (1965) says that in Hanoi, words spelled with ưu and ươu are pronounced /iw, iəw/, respectively, whereas other dialects in the Tonkin delta pronounce them as /ɨw/ and /ɨəw/. This observation is also made by Phạm (2008) and Kirby (2011).

When stops /p, t, k/ occur at the end of words, they have no audible release ([p̚, t̚, k̚]):

When the velar consonants /k, ŋ/ are after /u, o, ɔ/, they are articulated with a simultaneous bilabial closure [k͡p̚, ŋ͡m] (i.e. doubly articulated) or are strongly labialized [k̚ʷ, ŋʷ].

The pronunciation of syllable-final ch and nh in Hanoi Vietnamese has had different analyses. One analysis, that of Thompson (1965) has them as being phonemes /c, ɲ/, where /c/ contrasts with both syllable-final t /t/ and c /k/, and /ɲ/ contrasts with syllable-final n /n/ and ng /ŋ/. Final /c, ɲ/ is, then, identified with syllable-initial /c, ɲ/.

Another analysis has final ⟨ch⟩ and ⟨nh⟩ as representing different spellings of the velar phonemes /k/ and /ŋ/ that occur after upper front vowels /i/ (orthographic ⟨i⟩) and /e/ (orthographic ⟨ê⟩). This analysis interprets orthographic ⟨ach⟩ and ⟨anh⟩ as an underlying /ɛ/, which becomes phonetically open and diphthongized: /ɛk/ → [ăjk̟̚], /ɛŋ/ → [ăjŋ̟].^[10] This diphthongization also affects ⟨êch⟩ and ⟨ênh⟩: /ek/ → [ə̆jk̟̚], /eŋ/ → [ə̆jŋ̟].

Arguments for the second analysis include the limited distribution of final [c] and [ɲ], the gap in the distribution of [k] and [ŋ] which do not occur after [i] and [e], the pronunciation of ⟨ach⟩ and ⟨anh⟩ as [ɛc] and [ɛɲ] in certain conservative central dialects,^[11] and the patterning of [k]~[c] and [ŋ]~[ɲ] in certain reduplicated words. Additionally, final [c] is not articulated as far forward as the initial [c]: [c] and [ɲ] are pre-velar [k̟, ŋ̟] with no alveolar contact.^[12]

The first analysis closely follows the surface pronunciation of a slightly different Hanoi dialect than the second. In this dialect, the /a/ in /ac/ and /aɲ/ is not diphthongized but is actually articulated more forward, approaching a front vowel [æ]. This results in a three-way contrast between the rimes ăn [æ̈n] vs. anh [æ̈ɲ] vs. ăng [æ̈ŋ]. For this reason, a separate phonemic /ɲ/ is posited.

The following rimes ending with velar consonants have been diphthongized in the Hanoi dialect, but /i/, /u/ and /ɨ/ are more open:^[11]

With the above phonemic analyses, the following is a table of rimes ending in /n, t, ŋ, k/ in the Hanoi dialect:

While the variety of Vietnamese spoken in Hanoi has retained finals faithfully from Middle Vietnamese, the variety spoken in Ho Chi Minh City has drastically changed its finals. Rimes ending in /k, ŋ/ merged with those ending in /t, n/, respectively, so they are always pronounced /t, n/, respectively, after the short front vowels /i, e, a/ (only when /a/ is before "nh"). However, they are always pronounced /k, ŋ/ after the other vowels /u, uː, o, ɔ, iː, ɨː, ɨ, aw, a, aː, ɛ, ə, əː/. After rounded vowels /aw, u, o/, many speakers close their lips, i.e. they pronounce /k, ŋ/ as [k͡p, ŋ͡m].^[11] Subsequently, vowels of rimes ending in labiovelars have been diphthongized, while vowels of rimes ending in alveolar have been centralized.^[13] Otherwise, some Southern speakers distinguish /k, ŋ/ and /t, n/ after /u, uː, o, ɔ, iː, ɨː, ɨ, aw, a, aː, ɛ, ə, əː/ in formal speech, but there are no Southern speakers who pronounce "ch" and "nh" at the end of syllables as /k, ŋ/.

The short back vowels in the rimes have been diphthongized and centralized, meanwhile, the consonants have been labialized. Similarly, the short front vowels have been centralized which are realized as central vowels /ă, ə, ɨ/ and the "unspecified" consonants have been affected by coronal spreading from the preceding front vowels which are surfaced as coronals (alveolar) /n, t/.^[11]

The other closed dialects (Hue, Quang Nam, Binh Dinh) which have also been merged in codas, but some vowels are pronounced differently in some dialects:

The ông, ôc rimes are merged into ong, oc as [ăwŋ͡m], [ăwk͡p̚] in many Southern speakers, but not with ôn, ôt as pronounced [oːŋ͡m], [oːk͡p̚]. The oong, ooc and eng, ec rimes are few and are mostly loanwords or onomatopoeia. The ôông, ôôc (oong, ooc, eng, ec, êng, êc as well) rimes are the "archaic" form before becoming ông, ôc by diphthongization and still exist in the North Central dialect in many placenames. The articulation of these rimes in the North Central dialect are [oːŋ], [oːk̚] without a simultaneous bilabial closure or labialization.^[17]

With the above phonemic analyses, the following is a table of rimes ending in /n, t, ŋ, k, ŋ͡m, k͡p/ in the Ho Chi Minh City dialect:

Vietnamese vowels are all pronounced with an inherent tone. Tones differ in

• pitch
• length
• contour melody
• intensity
• phonation (with or without accompanying constricted vocal cords)

Unlike many Native American, African, and Chinese languages, Vietnamese tones do not rely solely on pitch contour. Vietnamese often uses instead a register complex (which is a combination of phonation type, pitch, length, vowel quality, etc.). Thus, it may be more accurate to categorize Vietnamese as a register language rather than a "pure" tonal language.^[18]

In Vietnamese orthography, tone is indicated by diacritics written above or below the vowel.

There is much variation among speakers concerning how tone is realized phonetically. There are differences between varieties of Vietnamese spoken in the major geographic areas (northern, central, southern) and smaller differences within the major areas (e.g. Hanoi vs. other northern varieties). In addition, there seems to be variation among individuals. More research is needed to determine the remaining details of tone realization and the variation among speakers.

The six tones in the Hanoi and other northern varieties are:

• The ngang tone is level at around the mid level (33) and is produced with modal voice phonation (i.e. with "normal" phonation). Alexandre de Rhodes (1651) describes this as "level"; Nguyễn (1997) describes it as "high (or mid) level".

• The huyền tone starts low-mid and falls (21). Some Hanoi speakers start at a somewhat higher point (31). It is sometimes accompanied by breathy voice (or lax) phonation in some speakers, but this is lacking in other speakers: bà = [ɓa˨˩].^[19] Alexandre de Rhodes (1651) describes this as "grave-lowering"; Nguyễn (1997) describes it as "low falling".

• The hỏi tone starts a mid level and falls. It starts with modal voice phonation, which moves increasingly toward tense voice with accompanying harsh voice (although the harsh voice seems to vary according to speaker). In Hanoi, the tone is mid falling (31). In other northern speakers, the tone is mid falling and then rises back to the mid level (313 or 323). This characteristic gives this tone its traditional description as "dipping". However, the falling-rising contour is most obvious in citation forms or when syllable-final; in other positions and when in fast speech, the rising contour is negligible. The hỏi also is relatively short compared with the other tones, but not as short as the nặng tone. Alexandre de Rhodes (1651) describes this as "smooth-rising"; Nguyễn (1997) describes it as "dipping-rising".

• The ngã tone is mid rising (35). Many speakers begin the vowel with modal voice, followed by strong creaky voice starting toward the middle of the vowel, which is then lessening as the end of the syllable is approached. Some speakers with more dramatic glottalization have a glottal stop closure in the middle of the vowel (i.e. as [VʔV]). In Hanoi Vietnamese, the tone starts at a higher pitch (45) than other northern speakers. Alexandre de Rhodes (1651) describes this as "chesty-raised"; Nguyễn (1997) describes it as "creaking-rising".

• The sắc tone starts as mid and then rises (35) in much the same way as the ngã tone. It is accompanied by tense voice phonation throughout the duration of the vowel. In some Hanoi speakers, the ngã tone is noticeably higher than the sắc tone, for example: má = ˧˦ (34); mã = ˦ˀ˥ (45). Alexandre de Rhodes (1651) describes this as "acute-angry"; Nguyễn (1997) describes it as "high (or mid) rising".

• The nặng tone starts mid or low-mid and rapidly falls in pitch (32 or 21). It starts with tense voice that becomes increasingly tense until the vowel ends in a glottal stop closure. This tone is noticeably shorter than the other tones. Alexandre de Rhodes (1651) describes this as "chesty-heavy"; Nguyễn (1997) describes it as "constricted".

In Southern varieties, tones ngang, sắc, huyền have similar contours to Northern tones; however, these tones are produced with normal voice instead of breathy voice.

The nặng tone is pronounced as low rising tone (12) [˩˨] in fast speech or low falling-rising tone (212) [˨˩˨] in more careful utterance.

The ngã and hỏi tone are merged into a mid falling-rising (214) [˨˩˦], which is somewhat similar to the hỏi tone of the non-Hanoi Northern accent mentioned above. This merged hỏi–ngã tone is characteristic of Southern Vietnamese accents.^[22][23]

North-central and Central Vietnamese varieties are fairly similar with respect to tone although within the North-central dialect region there is considerable internal variation.

It is sometimes said (by people from other provinces) that people from Nghệ An pronounce every tone as a nặng tone.

An older analysis assumes eight tones rather than six.^[25] This follows the lead of traditional Chinese phonology. In Middle Chinese, syllables ending in a vowel or nasal allowed for three tonal distinctions, but syllables ending with /p/, /t/ or /k/ had no tonal distinctions. Rather, they were consistently pronounced with a short high tone, which was called the entering tone and considered a fourth tone. Similar considerations lead to the identification of two additional tones in Vietnamese for syllables ending in /p/, /t/, /c/ and /k/. These are not phonemically distinct from the sắc and nặng tones, however, and hence not considered as separate tones by modern linguists and are not distinguished in the orthography.

According to Hannas (1997), there are 4,500 to 4,800 possible spoken syllables (depending on dialect), and the standard national orthography (Quốc Ngữ) can represent 6,200 syllables (Quốc Ngữ orthography represents more phonemic distinctions than are made by any one dialect).^[26] A description of syllable structure and exploration of its patterning according to the Prosodic Analysis approach of J.R. Firth is given in Henderson (1966).^[27]

The Vietnamese syllable structure follows the scheme:

(C₁)(w)V(G|C₂)+T

where

In other words, a syllable has an obligatory nucleus and tone, and can have an optional consonant onset, an optional on-glide /w/, and an optional coda or off-glide.

More explicitly, the syllable types are as follows:

C₁: Any consonant may occur in as an onset with the following exceptions:

• /p/ does not occur in native Vietnamese words

w: the onglide /w/ (sometimes transcribed instead as labialization [ʷ] on a preceding consonant):

• does not occur after labial consonants /ɓ, f, v, m/
• does not occur after /n/ in native Vietnamese words (it occurs in uncommon Sino-Vietnamese borrowings ^{[example needed]})

V: The vowel nucleus V may be any of the following 14 monophthongs or diphthongs: /i, ɨ, u, e, ə, o, ɛ, ə̆, ɔ, ă, a, iə̯, ɨə̯, uə̯/.

G: The offglide may be /j/ or /w/. Together, V and G must form one of the diphthongs or triphthongs listed in the section on Vowels.

• offglide /j/ does not follow the front vowels /i, e, ɛ, iə̯/
• offglide /w/ does not follow the rounded vowels /u, o, ɔ, uə̯/
• with some exceptions (such as khuỷu tay "elbow"), the offglide /w/ cannot occur if the syllable contains a /w/ onglide

C₂: The optional coda C₂ is restricted to labial, coronal, and velar stops and nasals /p, t, k, m, n, ŋ/, which cannot cooccur with the offglides /j, w/.

T: Syllables are spoken with an inherent tone contour:

• Six tone contours are possible for syllables with offglides /j, w/, closed syllables with nasal codas /m, n, ŋ/, and open syllables—i.e., those without consonant codas /p, t, k/.
• If the syllable is closed with one of the oral stops /p, t, k/, only two contours are possible: the sắc and the nặng tones.

Below is a table comparing four linguists' different transcriptions of Vietnamese vowels as well as the orthographic representation. Notice that this article mostly follows Han (1966), with the exception of marking short vowels short.

Thompson (1965) says that the vowels [ʌ] (orthographic â) and [ɐ] (orthographic ă) are shorter than all of the other vowels, which is shown here with the length mark [ː] added to the other vowels. His vowels above are only the basic vowel phonemes. Thompson gives a very detailed description of each vowel's various allophonic realizations.

Han (1966) uses acoustic analysis, including spectrograms and formant measuring and plotting, to describe the vowels. She states that the primary difference between orthographic ơ & â and a & ă is a difference of length (a ratio of 2:1). ơ = /ɜː/, â = /ɜ/; a = /ɐː/, ă = /ɐ/. Her formant plots also seem to show that /ɜː/ may be slightly higher than /ɜ/ in some contexts (but this would be secondary to the main difference of length).

Another thing to mention about Han's studies is that she uses a rather small number of participants and, additionally, although her participants are native speakers of the Hanoi variety, they all have lived outside of Hanoi for a significant period of their lives (e.g. in France or Ho Chi Minh City).

Nguyễn (1997) has a simpler, more symmetrical description. He says that his work is not a "complete grammar" but rather a "descriptive introduction." So, his chart above is more a phonological vowel chart rather than a phonetic one.

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